1. Field of the Invention
The present invention relates to a magnetic recording and reproduction apparatus for magnetically recording and/or reproducing information by using a magnetic tape as a recording medium.
2 Description of the Related Art
As shown in FIG. 1, in a video tape recorder (to be referred to as a "VTR" hereinafter) for current standard television systems (a term "television" will be abbreviated to as a "TV" hereinafter) such as an NTSC system, a
system, and an SECAM system, a recording circuit 25 and a reproduction circuit 29 provided at arbitrary positions except for a position of a rotary drum portion are coupled to a magnetic head 27 (in FIG. 1, a recording and reproduction head to be used in both recording and reproduction is shown) provided in the rotary drum portion via a rotary transformer 26. A recording current is supplied from the recording circuit 25 to the magnetic head 27 via the rotary transformer 26, and a reproduced signal extracted from the magnetic head 27 is supplied to the reproduction circuit 29 via the rotary transformer 26, thereby performing recording and reproduction for magnetic tape 28.
In recent years, wide-band, high-transmission rate VTRs (to be referred to as "wide-band/high-transmission rate VTRs" hereinafter) such as a high-resolution VTR and a digital VTR of a current TV system have been developed and put into practical use. In these wide-band/high-transmission rate VTRs, an inductance of a rotary transformer, a stray capacitance, and a cable coupling capacitance between the rotary transformer and a magnetic head, which are not so problematic in conventional VTRs, have been considered as problems. That is, transmission characteristics of an electromagnetic conversion system in magnetic recording are determined by a resonance frequency obtained by inductances of a magnetic head and a rotary transformer and the stray capacitance including an input capacitance of a reproduction circuit in a recording system, and is determined by a resonance frequency obtained by an inductance of the magnetic head, an inductance of the rotary transformer, and the stray capacitance including the input capacitance of the reproduction circuit in a reproduction system. In order to realize a wide-band/high-transmission rate VTR, therefore, no rotary transformer is desirably interposed between the magnetic head and the recording and reproduction circuits.
In a VTR of this type, therefore, as described in "Technical Bulletin of Institute of Electronics, Information and Communication Engineers", MR85-54, a recording circuit and a reproduction circuit are mounted in a rotary drum portion and connected directly to a magnetic head without using a rotary transformer, thereby widening recording and reproduction bands.
In addition, bands of a rotary transformer for transmitting signals between the rotary drum portion and an external portion (between the rotary drum portion and the other portion), a driver circuit for driving the rotary transformer, and a receiver circuit for receiving signals from the rotary transformer must be simultaneously widened. That is, as the recording and reproduction bands are determined in accordance with the input capacitances of the magnetic head and the reproduction circuit, a transmission band of the rotary transformer is determined in accordance with the inductance of the rotary transformer and the input capacitance or the stray capacitance of the receiver circuit. Therefore, a cable having a large capacitance, e.g., a coaxial cable having a large capacitance cannot be used to couple the driver and receiver circuits to the rotary transformer. In order to realize a wide band of the rotary transformer, therefore, the driver and receiver circuits must be mounted close to the rotary transformer. As a result, a scanner (an entire drum mechanism portion including a "rotary drum" and a "stationary drum" will be referred to as a "scanner" hereinafter) is complicated and enlarged since the driver and receiver circuits of the rotary transformer are mounted.
In addition, as described in "National Convention Record of the Institute of Television Engineers of Japan", Vol. 10, No. 41; VR87-S; T. Eguchi et al.; January, 1987, a VTR of this type must have at least six magnetic heads including those for normal reproduction and special-purpose reproduction. For example, a D-1 format 525 digital VTR employs 16 magnetic heads.
A rotary transformer is normally used for signal transmission between a rotary drum portion and an external portion (between the rotary drum portion and the other portion), and the number of channels of the rotary transformer must correspond to the number of magnetic heads mounted in the rotary drum. If, however, rotary transformers are mounted in a scanner in a number corresponding to the number of multi-channel magnetic heads, a mechanism of the scanner is enlarged and complicated, resulting in insufficient mechanical precision of each portion. Although a recording or reproduction circuit must be provided in a number corresponding to the number of magnetic heads similar to the rotary transformer, it can be made compact and light by adopting an IC arrangement. Since, however, the rotary transformer must have a wide range and a low crosstalk between channels, its miniaturization is limited.
In order to simplify an arrangement of the mechanism of the scanner and that of an electronic circuit including the recording and the reproduction circuits, therefore, the number of channels of the rotary transformer must be reduced.
In addition, since the recording and reproduction circuits corresponding to the multi-channel magnetic head are mounted, power consumption is increased. Furthermore, since thermal expansion is caused in each mechanism portion of the scanner due to heat generated by circuit elements, precision of the mechanism is degraded. Therefore, low power consumption is also required for the recording and reproduction circuits to be mounted in the rotary drum and a circuit portion at the stationary drum side.